1. Field of the Invention
This invention relates to electronic components which utilize a substantially lead-free interconnect process when forming an electronic module.
2. Description of Related Art
As the circuit density increases on integrated circuit devices such as silicon microprocessors, there is a need for high density interconnection between such a device and a chip carrier to which these devices are typically attached. Traditional methods of joining using solder ball arrays may become difficult with such dense circuitry.
Typically, solder ball arrays require fluxes when joining lead based solders. With connection densities reaching about 150 .mu.m or below, it becomes difficult to clean such fluxes. Without effective flux cleaning, underfill materials which are used to enhance reliability of the resulting electronic module run the risk of delaminating. The use of lead based solder also increases the difficulties in disposing of any waste.
The circuit density also poses problems with shorting between adjacent solder balls particularly on chip carriers having camber or deformities. Typical chip carriers such as a ceramic substrate exhibit about 25 to about 50 .mu.m camber as measured from a flat surface of the substrate. When a device with solder balls is joined to such a carrier, some of the solder balls contact the mating pads. Due to the wetting action of the solder the device is pulled down and remaining solder balls which make contact further pull down the chip. As a result, after joining, many of the solder balls are in closer proximity to each other and may be contacting each other leading to shorts.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a method of interconnecting high circuit density electronic components utilizing substantially lead-free interconnects which do not require flux and takes into account the deformities on a substrate surface.
It is another object of the present invention to provide an electronic module having high circuit density electronic components which utilizes substantially lead-free interconnects which do not require flux and takes into account the deformities on a substrate surface.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.